Controlled stacking of different two-dimensional(2D)atomic layers hold great promise for significantly optimizing the optical properties of 2D materials and broadening their applications.Here,vertical 2D MoS2/Bi2Te3 heterostructures with high crystallinity and optical quality have been successfully constructed,through drop-casting 2D Bi2Te3 flakes on chemical vapor deposition(CVD)-grown MoS2 flakes.Based on our homebuilt micro Z-scan and pump-probe measurement,we precisely investigated and compared the nonlinear optical(NLO)performance of an individual micro-sized MoS2 flake before and after stacking 2D Bi2Te3 nanoplates.Moreover,layer-dependent ultrafast carrier dynamics of CVD-grown MoS2 flakes were also explored.Owing to the efficient charge transfer from the monolayer(1 L)MoS2 to 2D Bi2Te3,the 1L MoS2/Bi2Te3 heterostructure demonstrated excellent NLO performance with superior nonlinear saturable absorption coefficient and ultrashort carrier lifetime.Our work greatly enriches our understanding of 2D heterostructure and paves the way for designing new type of tunable 2D photonics materials by combining the optical advantages of different 2D materials.